A traffic light detection device configured to detect a traffic light from an image shot with a camera has heretofore been known (see Japanese Patent Application Publication No. 2005-301518). According to Japanese Patent Application Publication No. 2005-301518, a signal lamp candidate is detected from an image based on a color and a shape of a signal lamp, and it is determined whether or not the signal lamp candidate blinks at a predetermined cycle.
When a vehicle that mounts a camera is moving, a position of an edge portion included in an image shot during the movement and having a luminance difference equal to or above a predetermined value also moves accordingly. This causes a step response of luminance in a region where the edge portion is moving, and generates noise having wide frequency components. When pixels with luminances varying at a predetermined cycle are extracted as a lamp, the noise having a wide frequency component is apt to be falsely recognized as such a lamp.